DARPA has officially announced a new DARPA Challenge, the Spectrum Challenge - a new competition to design effective software-defined radio protocols using USRPs. Teams interested in combining signal processing and communication techniques to build robust radio systems in a competitive and cooperative setting are encouraged to participate. Details for the Spectrum Challenge can be found at www.darpa.mil/spectrumchallenge<http://www.darpa.mil/spectrumchallenge>